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Help Your Employees Protect Against Pathogens
Food handlers, processors bring pathogens in
by Charles Giambrone, MS
The media and the public generally focus first on the actual pathogen when a foodborne illness occurs, eventually turning their focus to the source of the illness. Often, an infected person causes the outbreak directly—or even indirectly—through a series of improper actions or inactions. Humans can be considered the parameter of these illnesses.
The word “parameter” has many definitions. In math and statistics, it is a constant or variable term or a set of independent variables or a variable entering into the mathematical form. More generally, a parameter is a characteristic or a factor. Humans are both a constant and a variable factor in the epidemiology of foodborne illnesses.
The issue of food safety can be considered from a microbial ecological perspective, with foodborne disease falling into two key niches or source environments that people provide: soil and water, and non-fecal body fluids.
This discussion will exclude fecal and dermal, because these two sources of pathogenic contamination can be lengthy topics. And much has been described and discussed regarding good manufacturing practices (GMPs) pertaining to personal hygiene, specifically hand washing and sanitizing, which are primary control measures for fecal and dermal transmission routes. In every instance, however, proper control and prevention measures ultimately deal with the source vectors of the pathogen.
Each of these sources can and do involve multiple transmission routes. For example, in some cases, a single “lone wolf” causes the entire outbreak or contaminates other food workers who create the epidemiological thread. In other outbreaks, the food worker provides a low level of contamination through one of the four sources, and environmental conditions permit its proliferation.
These have been organized into categories of outbreaks based on the infective behavior or pattern of human-mediated contamination resulting in foodborne illnesses, as well as subsets of categories, because of the variable and dynamic nature of food handling and processing systems.1
These sources have both unique and overlapping microbial pathogens of concern, another reason epidemiological investigations are not always crystal clear about the source. Does the implicated Staphylococcus aureus or Salmonella serotype come from a person, an animal, or a secondary source? Clearly, specific viral and bacterial pathogens cause the majority of human-mediated foodborne disease.
Viruses are implicated in roughly 60% of all human-mediated foodborne outbreaks. The noroviruses and hepatitis A are involved in more than 30% and 10%, respectively, of all the viral-associated outbreaks. Approximately 35% of all outbreaks involve these pathogens: Salmonella spp., Staphylococcus aureus, Shigella spp., groups A and G Streptococcus, Vibrio cholerae, Campylobacter jejuni, and E. coli 0157:H7.2 Noroviruses have been found in every key food category or group, as have Salmonella, S. aureus, and Streptococcus spp.2,3
Soil and Waterborne
Both the food industry, with its good agricultural practices, and the food processing, food service, and retail industries have measures in place to control inadvertent transfer of soil-borne and other environmental carriers. Unfortunately, lack of enforcement or control enables pathogens to contaminate products and cause illness in consumers.
Clothing, jewelry, and street shoes are notorious carriers of fomites, the objects or materials that serve as carriers from one person to another or to a food product. In many food processing plants, fomite control through prohibition of street clothes and shoes is one of the most successful GMP tools available.
Street shoes will bring in copious amounts of fomites containing Listeria species and other non-spore-forming gram-positive bacteria, including L. monocytogenes, Streptococcus, and Staphylococcus.
In some food plant operations, however, smocks are required, but street shoes can be worn with no plastic or rubber covers. This lack of control can and does increase in the service and retail segments of the food chain, resulting in a flood of fomites that can potentially spread food pathogens of all types. Key vectors of fomites include:
- Shoes, street clothes, and rings. Street shoes will bring in copious amounts of fomites containing Listeria species and other non-spore-forming gram-positive bacteria, including L. monocytogenes, Streptococcus, and Staphylococcus. If the soil is moist or wet, enteric microbes like E. coli 0157:H7, Salmonella, and even Shigella can be transferred into a food handling/processing environment. If the soil fomites are from more arid sources, the fungal and bacterial spore-forming pathogens, including Clostridium botulinum and Bacillus cereus, will ride in on them.
- Carpets, anti-fatigue mats, or a white rag used to improperly wipe a food service counter or table can transmit pathogens. All microbial carriers usually have a nice layer of organic material that shields the pathogenic microbes from environmental stresses while also providing nutrients. Several studies have established that non-spore-forming microbial pathogens like Staphylococcus and Salmonella species can survive more than 24 hours on dried surfaces.4 Other enteric non-spore-forming pathogens like Enterococcus faecium can survive up to seven days.5
The transfer of food pathogens via fomites is accelerated in food processing plants or food service prep kitchens. The microbial ecological dynamics of these specific environments dictate which pathogens will prosper. In general, wet or humid environments with water activities (aw) above 0.90 will enable a lot of non-spore-forming pathogens to prosper.
Dry food handling environments are not guaranteed to be pathogen free. Rather, a shift occurs in the microbial pathogen profile to spore formers and to non-spore formers that readily adapt to drier conditions. These include Staphylococcus aureus, hepatitis A, and the ubiquitous norovirus.6,7
Control programs delineated in GMPs, which should include restriction of street clothes and shoes, proper utilization of hair nets and gloves, and prevention of food handling by ill workers, will markedly improve control of fomite-mediated pathogens.
Environmental control measures for fomite-mediated pathogens also include proper sanitation procedures for all environmental surfaces. This includes use of proper cleaners and sanitizers, as well as both fogging and foaming type disinfection.
Oral Tract Body Fluids
As with many communicable diseases, respiratory fluids excreted, sneezed, or coughed from the oral and nasal passages are a major source of food product cross contamination from humans. In addition to the numerous viral particles expelled from respiratory tract fluids, which can include carriers of hepatitis A, there are several key bacterial pathogens of concern.
While tuberculosis carriers in industrialized nations are less prevalent than a century ago, there are more antibiotic-resistant mycobacterial strains. With the preponderance of workers from underdeveloped nations in many food plants, transfer of tuberculosis strains between workers and contamination of perishable ready-to-eat food products are possible in a food operation that lacks a proper screening program for pathogenic strains of tuberculosis.
Several key gram-positive pathogens derived from respiratory tract fluids cannot be screened by even the most thorough employee health programs. Staphylococcal strains, specifically S. aureus, are prevalent in food workers’ respiratory fluids; an estimated 20% of food workers carry toxigenic strains of S. aureus. Other studies have found higher percentages of toxigenic strains. A study of airline catering food handlers found that noses and nasal secretions had higher positive rates of S. aureus than hands.8 These toxigenic strains include methicillin-resistant Staphylococcus aureus, which can be directly transferred to food from workers by fomites and respiratory fluids.
Streptococcal pathogenic strains are also major colonizers of respiratory tract fluids. Most of the group A beta-hemolytic Streptococcus found in food workers are colonized by these pathogens rather than being caused by illness. Sneezing can be a primary mode of streptococcal transmission. Although sneezing or transference of nasal secretions onto food products is the source of streptococcal contamination, it is typically the holding conditions of ready-to-eat handled food products that permit the streptococcal pathogenic strains to grow, leading to foodborne illness outbreaks.9
The most effective control measures involve proper GMP training in personal hygiene, with recognition of the critical role played by respiratory illnesses, cuts, and lesions in transmission to food products of these staphylococcal and streptococcal pathogenic strains.
Urinary, Upper GI Fluids
Excluding urinary tract infections that cause marked illness in food workers, the infectious agents that are a concern include Salmonella strains such as S. typhi from asymptomatic carriers. Hepatitis A caused by intentional contamination of food product by a food service worker has been documented in urine. Such outbreaks, while rare, underscore the need for proper personal hygiene in food workers who have asymptomatic infections.
Upper gastrointestinal tract fluid, specifically vomit, can create a variety of cross contamination vectors on clothing, in restrooms, and on hands or skin. The possible pathogens include norovirus, Salmonella, S. aureus and B. cereus.
If the food handler or worker accidentally vomits in a food environment, a major contributing factor of the viral or bacterial pathogen cross contamination is aerosolization of the pathogenic agent in the vomitus. Another factor can be incomplete decontamination of the worker. Sometimes an employee trying to hide his illness or vomiting episode will improperly clean and sanitize the toilet or sink. If food product is later cooled in the same sink, the food will be contaminated, causing a significant outbreak.10 Contamination can also be caused by unchanged clothing after vomiting or by inadequate personal hygiene. ■
Giambrone is the senior technical support manager at Rochester Midland Corp. and is also a qualified SQF consultant. Reach him at firstname.lastname@example.org.
- Todd EC, Greig JD, Bartleson CA, et al. Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 3. Factors contributing to outbreaks and description of outbreak categories. J Food Prot. 2007;70(9):2199-2217.
- Greig JD, Todd EC, Bartleson CA, et al. Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 1. Description of the problem, methods, and agents involved. J Food Prot. 2007;70(7):1752-1761.
- Todd EC, Greig JD, Bartleson CA, et al. Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 2. Description of outbreaks by size, severity, and settings.J Food Prot. 2007;70(8):1975-1993.
- Dawson P, Han I, Cox M, et al. Residence time and food contact time effects on transfer of Salmonella typhimurium from tile, wood, and carpet: testing the five-second rule. J Appl Microbiol. 2007;102(4):945-953.
- Noskin GA, Stosor V, Cooper I, et al. Recovery of vancomycin-resistant enterococci on fingertips and environmental surfaces. J Infect Control Hosp Epidemiol. 1995;16(10):577-581.
- Sattar SA, Jason T, Bidawid S, et al. Foodborne spread of hepatitis A: Recent studies on virus survival, transfer and inactivation. Can J Infect Dis. 2007;11(3):159-163.
- Sattar SA, Lloyd-Evans N, Springthorpe VS, et al. Institutional outbreaks of rotavirus diarrhoea: potential role of fomites and environmental surfaces as vehicles for virus transmission. J Hyg [London]. 1986;96(2):277-289.
- Hatakka M, Björkroth KJ, Asplund K, et al. Genotypes and enterotoxicity of Staphylococcus aureus isolated from hands and nasal cavities of flight-catering employees. J Food Prot. 2000;63(11):1487-1491.
- Todd EC, Greig JD, Bartleson CA, et al. Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 5. Sources of contamination and pathogen excretion from infected persons. J Food Prot. 2008;71(12):2582-2595.
- Patterson W, Haswell P, Fryers PT, et al. Outbreak of small round structured virus gastroenteritis arose after kitchen assistant vomited. Commun Dis Rep CDR Rev. 1997;7(7):R101-R103.